survfit.object {survival}R Documentation

Survival Curve Object


This class of objects is returned by the survfit class of functions to represent a fitted survival curve.

Objects of this class have methods for the functions print, summary, plot, points and lines. The print.survfit method does more computation than is typical for a print method and is documented on a separate page.


The following components must be included in a legitimate survfit object.

the time points at which the curve has a step.
the number of subjects at risk at t.
the number of events that occur at time t.
the estimate of survival at time t+0. This may be a vector or a matrix.
if there are multiple curves, this component gives the number of elements of the time etc. vectors corresponding to the first curve, the second curve, and so on. The names of the elements are labels for the curves.
the standard error of the cumulative hazard or -log(survival).
upper confidence limit for the survival curve.
lower confidence limit for the survival curve.
the approximation used to compute the confidence limits.
the level of the confidence limits, e.g. 90 or 95%.
the returned value from the na.action function, if any. It will be used in the printout of the curve, e.g., the number of observations deleted due to missing values.
the call that produced the object.


Survfit objects that contain multiple survival curves can be subscripted. This is most often used to plot a subset of the curves. Usually a single subscript will be used. In one particular case – survival curves for multiple covariate values, from a Cox model that includes a strata statement – there is a matrix of curves and 2 subscripts may be used. (In this case summary.survfit will also print the data as a matrix).

See Also

survfit, plot.survfit, summary.survfit, print.survfit.

[Package survival version 2.17 Index]